In general, various processes, e.g., a film forming process or a pattern etching process are repeatedly performed on a semiconductor wafer to manufacture semiconductor devices. With increased requirements for high-integration and high-miniaturization of semiconductor devices, a line width or hole diameter of the device is getting smaller. Further, conventionally, an aluminum alloy is widely used as a wiring material or a burying material. However, recently, there is a tendency to use tungsten (W), copper (Cu) or the like for meeting the requirements of a fine line width, a fine hole diameter and a high operating speed.
Further, when a metal material such as Al, W and Cu is used as a wiring material or a burying material for a contact hole, silicon may be diffused between an insulating material of, e.g., a silicon oxide (SiO2) film and the metal materials. In order to prevent the diffusion of silicon or improve adhesivity of the film, a barrier layer is provided at a boundary between an insulating layer and a conductive layer formed thereunder. A Ta film, a TaN film, a Ti film, a TiN film or the like were widely known as the barrier layer. Further, a thin film containing metal such as Cu, Ti, Ta or the like is generally formed by using a plasma sputtering method and a plasma film forming apparatus (see, e.g., Japanese Patent Application Publication No. 2001-250816 or 2007-214387).
In the plasma film forming apparatus, for instance, a mounting table having a chuck electrode and a heater is placed in a vacuum evacuable processing chamber and a semiconductor wafer is mounted on the mounting table. The semiconductor wafer is attracted and held on the mounting table by an electrostatic force generated by a high voltage applied to the chuck electrode. In this state, metal ions generated from a metal target by a plasma are attracted to the mounting table by a high frequency bias power to form, e.g., a metal thin film on the semiconductor wafer. Further, the mounting table is provided with a cooling jacket in addition to the heater. The heater and the cooling jacket are controlled according to the amount of heat supplied to the semiconductor wafer from the plasma side such that the semiconductor wafer is maintained at a temperature suitable for film formation.
A conventional mounting table structure is illustrated in FIG. 10. A mounting table 2 includes a metal base 6 having a cooling jacket 4 and a thin ceramic heater 8 installed on the base 6. A chuck electrode 10 and a heater 12 are embedded in the ceramic heater 8. A semiconductor wafer W is mounted on the ceramic heater 8 to be attracted and held thereon by an electrostatic force. Further, the ceramic heater 8 is strongly attached to a top surface of the base 6 by an adhesive 14.
In the above-mentioned apparatus, any particular problem does not occur in a conventional case in which the design criterion is not very strict. However, when the design criterion becomes strict due to high integration and miniaturization of the semiconductor devices, it is required that the quality and characteristics of a metal film are improved. Accordingly, for example, in order to prevent contamination of the metal film due to foreign matter, it is required to discharge impurities attached to the surface of the processing chamber or an inner structure by outgassing by evacuating the processing chamber to a high vacuum level prior to the film formation. However, the adhesive 14 continuously emits an impurity gas of silicon compounds such as siloxane. Accordingly, it is difficult that the processing chamber is maintained at a high vacuum level and in a clean state.
Further, in order to improve the quality and characteristics of a thin film, it is required to perform a film forming process at a high process temperature of, e.g., about 400° C. However, the heat resistant temperature of the adhesive is very low, e.g., about 80° C. Thus, the adhesive cannot be used.
Further, there is a mounting table structure wherein a chuck electrode or a heater is buried in a mounting table by thermal spraying. However, also in this case, a thermally sprayed portion has a heat resistant temperature of at most about 80° C. and, thus, cannot endure the high temperature.